This invention relates to a flow delivery system used for pressurizing seals in a turbo machine.
Turbo machines, such as a turbofan engine used in aircraft, incorporate carbon seals to separate a bearing compartment from a buffer compartment. The bearing compartment includes bearings supporting, for example, a turbine for rotation relative to a housing of the engine. The bearing compartment contains a lubricant that lubricates the bearings. The buffer compartment contains pressurized air that leaks past the seals which prevents the lubricant from weeping past the seals.
The carbon seals require a predetermined differential pressure across the seal in order to prevent leakage of lubricant past the seal. One problem is that lubrication has been known to leak past the carbon seals at idle conditions, because of an inadequate pressure differential across the seals.
The buffer compartment consists of a body which is generally cylindrical. Compressor bleed air flows into the body in a direction normal to a plane that is tangential to the body. As a result, a stagnation area forms within the body directly across from where the flow enters the body. This causes an uneven pressure distribution along the cylindrical wall of the body, and if one of the carbon seals is arranged near the cylindrical wall, the uneven pressure on the seal may result in leaks. Notwithstanding the position of the seal, the pressure in the buffer compartment is inadequate at idle.
Increased pressure is required within the buffer compartment in the vicinity of the carbon seals for the seals to be effective.